Question How to dive nitrox for the first time

[ttc008]

I got my nitrox cert in 2023 as a dry course at the end of a dive trip but haven't dove nitrox since yet. I want to try nitrox on my planned october trip to cebu (moalboal, oslob, malapascua) but honestly I don't think I remember much from the course.

I will certainly do a full review of the course materials before the trip which I think are still available because the cert was with SSI. However, from what little I do remember, apart from the theory and the science, nitrox doesn't change much "how" I dive except that I need to check the gas and set my computer to nitrox mode, right? If there's a lot more I should do in practice then I better shut up and go back to the first page of the textbook now, but I just want to get a basic sense of where I am at the moment. Thanks in advance!

 

[VsubT]

A couple of missing puzzle pieces:

- select the % O2 mix you will use based on the dive profile and available blends

- make sure you understand the maximum operating depth (MOD) limitations for the mix that you select

If those don’t make sense to you, talk to an instructor.

Lance

 

[Bjparris1990]

Just review maximum depth and make sure to change your computer. That should cover the two big parts.

 

[DiveLikeAMuppet]

- Check that the gas analyser is calibrated, calibrate it if needed
- Analyse your gas
- Calculate your MOD
- Correctly label your cylinder with MOD, gas mix, your name
- Plan your dive - you will now be limited by gas, not just NDL/no-stop times
- Discuss with your buddy what gas are they diving (hopefully similar gas mix, if they are on air and you use nitrox, change your buddy)
- Set computer(s) to correct gas mix

Repeat each day

 

[gamon]

-decide if you'll set your computer to PO2 1.4 or 1.6, I'm partial to 1.6 myself.

- understand which dives will benefit from Nitrox, those dives for which Nitrox may possibly offer a slight benefit, and those dives where you're just wasting your money filling your tanks with enriched air.

Generally speaking Nitrox is effective to the point of being worth the expense and extra steps when diving between 60-100' but there are exceptions outside that range.

 

[Sascha314]

To second each one:

There is no practical difference on the diving itself.

The only practical thing is to quantify and verify your actual mixture and how to take this into account by your dive computer.

However you have to take into account the additional limitations. You should remember at least the following details
- Maximal depth depending on your gas mixture (MOD, PPO2 limit)
- CNS oxygen clock, however mostly not relevant unless for many repetetive dives close and long at MOD limit.
- how your NDL changes

 

[halocline]

- Discuss with your buddy what gas are they diving (hopefully similar gas mix, if they are on air and you use nitrox, change your buddy)

There’s no need to ‘change your buddy’ if one diver is on air and the other on nitrox. Just make sure the buddy understands the MOD. This is recreational diving, there are mixed nitrox/air dive groups all the time.

 

[KatieMac]

@ttc008 why did you get your nitrox certification?

Some people do it to extend bottom times. I did it for enhanced safety/reduce nitrogen load. For this reason, I don't switch my computer's dive mode.

 

[Sascha314]

@ttc008
Some people do it to extend bottom times. I did it for enhanced safety/reduce nitrogen load. For this reason, I don't switch my computer's dive mode.

I would not suggest to do that. You will miss the mod warning, cns clock calculation and also the SAT/Desat calculation is off. Yeah you are always in a regime with less actual niteogen concentration, but why introduce a further uncertainty into a model?

For this case you can set a conservative setting on almost all computers. And just stay yourself away from NDL if you like.

 

[DiveLikeAMuppet]

There’s no need to ‘change your buddy’ if one diver is on air and the other on nitrox. Just make sure the buddy understands the MOD. This is recreational diving, there are mixed nitrox/air dive groups all the time.

It is very relevant in recreational diving. If your buddy is on air and you are on nitrox, you need to discuss no-stop times. You don’t want your buddy to shoot to the surface because OMG their computer showed 1 minute of deco while you were at 15 minutes NDL.

MODs might be different. Liveaboards - especially in Egypt - might call anything between 25% - 35 % as 32%. You never know when you might need to breathe your buddy’s gas.

Your buddy might be a slob who didn’t analyse their gas or dive at 1.6. So definitely worth having a discussion.